In the related arts, a tape accommodating cassette provided with three projections corresponding to tape-width sensors of a printer (tape printing apparatus) has been known as such a tape cartridge (see JP-7-214828).
In the printer, an installation portion of the tape accommodating cassette is provided with tape-width sensors configured with photo interrupters to respectively detect three projections. The tape-width sensors detect the presence or absence of three projections, respectively, and thus detects a tape width of a printing tape mounted in the tape accommodating cassette. In addition, the printer includes a cassette cover that opens/closes the installation portion of the tape accommodating cassette and a small mechanical switch that is provided at a position away from the installation portion and detects opening/closing of the cassette cover.